Stylish, wearing wig? Having second thoughts? (5)
I believe the answer is:
ruing
'having second thoughts?' is the definition.
(to rue something is to regret it)
'stylish wearing wig?' is the wordplay.
'stylish' becomes 'in'.
'wearing' is an insertion indicator.
'wig?' becomes 'rug' (rug is a slang term for a wig).
'in' going into 'rug' is 'RUING'.
(Other definitions for ruing that I've seen before include "feeling remorse" , "Feeling bad" , "Regretful" , "Feeling sorry for" , "Having second thoughts" .)